Police say 79 people are now dead or missing after the fire at Grenfell Tower in west London.
Police Commander Stuart Cundy gave the new figure during a statement outside Scotland Yard on Monday. The previous figure given was 58.
Cmdr Cundy says the new number may change as investigation continues.
Five people who had been reported missing after the disaster have been found safe and well, he said.
Cmdr Cundy said the search and recovery operation in the 24-storey tower continues, and it has been incredibly distressing for families.
He said that "it's hard to describe the devastation the fire has caused."
Cmdr Cundy added that authorities are investigating whether any crimes had been committed in the fire.
Two British officials said Sunday that new exterior cladding used in a renovation of Grenfell Tower may have been banned under UK building regulations.
Prime Minister Theresa May, under pressure for keeping a distance from angry residents on a visit to the charred remains of the 24-storey block last week, has previously said that the response to the disaster was "not good enough".
Her government is trying to make up ground in reacting to a fire that trapped people in their beds in the early hours of Wednesday, with many unable to escape as the flames raced up the building, cutting off exit routes and forcing some to jump.